Memory devices are typically provided as internal, semiconductor, integrated circuits in computers or other electronic devices. There are many different types of memory including volatile and non-volatile memory. Volatile memory can require power to maintain its information (e.g., data, error information, etc.) and includes random-access memory (RAM), dynamic random access memory (DRAM), and synchronous dynamic random access memory (SDRAM), among others. Non-volatile memory can provide persistent information by retaining stored information when not powered and can include NAND flash memory, NOR flash memory, read only memory (ROM), Electrically Erasable Programmable ROM (EEPROM), Erasable Programmable ROM (EPROM), and resistance variable memory such as phase change random access memory (PCRAM), resistive random access memory (RRAM), and magnetoresistive random access memory (MRAM), among others.
Memory devices can be combined together to form a solid state drive (SSD). A solid state drive can include non-volatile memory (e.g., NAND flash memory and NOR flash memory) and/or can include volatile memory (e.g., DRAM and SRAM) among various other types of non-volatile and volatile memory. Flash memory devices can include a charge storage structure, such as is included in floating gate flash devices and charge trap flash (CTF) devices, which may be utilized as non-volatile memory for a wide range of electronic applications. Flash memory devices may use a one-transistor memory cell that allows for high memory densities, high reliability, and low power consumption.
Memory cells in an array architecture can be programmed to a target charge storage state. For example, electric charge can be placed on or removed from the floating gate of a memory cell to put the cell into one of a number of charge storage states. For example, a single level cell (SLC) can be programmed to one of two charge storage states representing one of two units of information (e.g., 1 or 0). Multilevel memory cells (MLCs) can be programmed to one of more than two charge storage states. For example, an MLC capable of storing two units of information can be programmed to one of four charge storage states, an MLC capable of storing three units of information can be programmed to one of eight charge storage states, and an MLC capable of storing four units of information can be programmed to one of sixteen charge storage states. MLCs can allow the manufacture of higher density memories without increasing the number of memory cells since each cell can represent more than one unit of information, e.g., more than one bit. However, storing an increasing number of units of information in an MLC may increase a sensing time to resolve the stored units of information.